1. Field of the Invention
This invention relates generally to toy vehicles, and particularly relates to toy vehicles having treads, and to toy vehicles which may be operated in plural alternative modes depending upon the type of operating surface and upon the preference of the user.
2. Other Toy Vehicles
Other tread-driven toys, even those (if any) operating at selectable plural speeds, have in essence provided only a single mode of operation. We are unaware of any tread-driven toy having the "climbing-toy" characteristics that are defined in this document.
For example, the U.S. Pat. No. 4,306,375 mentioned above describes a toy vehicle which has startling climbing characteristics. It is able (traction permitting) to climb any grade on which it will not tip over backward--grades up to about 40.degree.--and to negotiate a vertical step taller than its tire radius. Its chassis is only slightly longer than, and less than twice as wide as, a "penlight" battery.
That toy, however, does not use tread drive. Moreover, that toy, by virtue of its relatively low operating speed, is particularly intended for use in its very unusual operating mode as a special-purpose climbing toy. The phrase "climbing toy" as used in this document means a toy, such as is described in the aforementioned patent, which has extraordinary climbing characteristics and certain features that are aimed at enhancing and maximizing those characteristics.
On the other hand, some earlier toys may have had two or more speeds, but to the best of our knowledge there have been no toys in which such plural speeds were provided for corresponding plural and essentially different operating purposes. As far as we know, prior miniature toy vehicles (other than the "climbing toy" described in the aforementioned patent) have been intended for and capable of self-propulsion across a generally level surface such as the floor or rug in a home, and at relatively low torques and high speeds. For purposes of verbal shorthand in this document we refer to such toys as "generally conventional toys," and to their operation as "generally conventional-toy operation."
Further, we know of no plural-speed powered toys whose speeds can be selected without picking up the entire toy vehicle to manipulate a selector of some kind underneath or inside the vehicle, and/or without using both hands to manipulate the selector. This limitation interferes with the free sway of illusion and fantasy in the use of a powered toy vehicle, by providing an obstacle to a toy user's native imagination. A "real" vehicle would not be raised from the street by its operator for speed changes, and a "real" vehicle is shifted using just one hand, so the illusion of playing with a "real" vehicle is dampened by the necessity to pick up the toy vehicle and to use both hands when changing speeds.
Yet another type of earlier toy, whicn undoubtedly antedates by centuries those toys just discussed, is the free-rolling vehicle which the user pushes, or allows to roll downhill. Ironically, such a primitive and simple use is not within the capabilities of many modern powered toys, because the motors and particularly the gear trains in many such toys are always engaged with the wheels. In the case of relatively large gear reductions, it can be very difficult to turn the wheels of such a vehicle: the gear train intrinsically resists being operated from its low-mechanical-advantage end.
In the toy vehicle of the earlier-mentioned patent, for instance, an extremely large mechanical-advantage value is obtained by use of a worm and worm gear. As is commonly known, the pitch of a worm is so shallow that it is quite impossible to rotate the worm by turning the worm gear: the worm gear simply binds against what is, in all practical effect, a stop. This effect is somewhat extreme in the toy vehicle of the earlier-mentioned patent, because of the use of a worm and worm gear, but it remains true that many or most powered toys cannot be freely rolled.
Again, we know of no powered toys whose wheels can be disengaged from their gear trains, to permit free rolling use, without picking the toy vehicle up and/or without using both hands to manipulate a selector. This too is an interference with the effectiveness of illusion in the use of a powered toy vehicle, as already described with respect to speed changes.